Only a small percentage of children exposed to environmental lead exhibit classical signs of lead poisoning, yet epidemiological studies indicate that subclinical lead exposure is associated with a greater than normal incidence of behavioral and neuro chemical disorders. In the proposed studies, the neonatal rat will be utilized to determine the effects of low level lead exposure on separate enzyme of functional indicators of brain development. The results of this investigation will answer essential questions concerning the relationship between lead dose, blood and brain lead levels and their effects on biochemical indices of blood-brain barrier development. These results will facilitate development of a relationship between disturbances produced in these studies and lead toxicity in children.